Language and communication impairments are key components of autism. Our laboratory has been conducting studies on preschool age children with autism examining early aspects of language processing. These studies have revealed critical differences in phonetic discrimination, social communication, and crossmodal processing between preschool age children with autism and mental-age and chronological-age matched groups of developmentally delayed (DD) and typically developing children. As these measures reflect abilities that emerge during infancy, these results signal the potential of early speech measures for identifying children with autism at a very young age. Furthermore, it is possible that these early measures of language and communication ability may prove to be very sensitive predictors of language outcome for children with autism. In the current proposal, we plan to examine these early speech measures - namely, (1) event-related brain potential measures of phonetic perception, (2) listening preference for speech versus mechanical-sounding auditory signals, and (3) vocal imitation abilities - in 18-24 month children with autism, and comparison groups of children with DD and typical development to determine whether such measures discriminate children with autism at an early age. Furthermore, we will assess their value in explaining individual differences and predicting language outcome at age 4 for children with autism.